Orientation dependence of valence-subband structures in GaAs-Ga1−xAlxAs quantum-well structures

Abstract

Valence‐subband structures of GaAs‐Ga_1−xAl_xAs quantum wells growth in the [001], [111], and [110] directions are calculated based on the bond‐orbital model. The effective mass for the first subband in (111)‐oriented quantum wells is found to be substantially smaller than that in (001)‐oriented quantum wells for well widths narrower than 70 Å. The subband structures of (110)‐oriented quantum wells display large anisotropy, with effective masses along two different in‐plane directions ([001] and [11̄0]) differing by almost one order of magnitude. It is also found that the Al composition has a strong effect on the hole effective mass. Implications of our results in device applications are also discussed.